Printed circuit boards having electronic components mounted on the surface thereof (or having components mounted thereon by placement of the leads of the components through holes in the circuit board) are currently mass produced in assembly line fashion using automated manufacturing equipment. Typically, at least three well-known manufacturing steps are involved in the manufacture of such printed circuit boards. A block diagram illustrating these steps and the required manufacturing equipment is shown in FIG. 1.
In the first step, solder paste or some other viscous material is applied to the surface of a printed circuit board in a specific pattern through a screen or stencil using a screen printing machine 10. Screen printing machines are well-known in the art and are commercially available from a number of sources, an example of which is the DEK model 265 GSX screen printing machine manufactured and sold by the assignee of the present invention DEK Printing Machines Limited.
Once the solder paste has been applied to the surface of the printed circuit board using screen printing machine 10, the next step involves placing the desired electronic components on the printed circuit board in particular locations. This task is performed quickly and automatically through the use of an automated component handling and placement machine 20, commonly referred to as a "pick and place" machine, shown in FIG. 1. Such machines typically have a placement head which picks up a series of components from a supply area and then places those components at desired locations on the printed circuit board (hence the name "pick-and-place" machines). Automated component handling and placement machines are well-known in the art and are commercially available from a number of sources, an example of which is the Universal Instruments model GSM machine, which is available from Universal Instruments Corporation in Binghamton, N.Y.
Once the desired electronic components have been placed by the automated component handling and placement machine 20 at the desired location on the board, a typical further manufacturing step is performed, which is commonly known as reflowing the solder paste. During this step, the printed circuit board having components placed thereon is placed inside a reflow oven 30 shown in FIG. 1 and the temperature inside the reflow oven 30 is raised. As a result of the increased temperature, the solder paste on the surface of the printed circuit board melts and wicks up the leads/ends of the electronics components, thereby creating a satisfactory electrical connection between the printed circuit board and the electronic components. Refold ovens are well-known in the art and are commercially available from a number of sources, including American Soltec, Inc. of Manchester, N.H.
During the manufacturing steps described above, which is just one example of the many different processes available in electronics manufacturing, the printed circuit boards are typically transported through and between the automated manufacturing equipment on what are commonly called rails, denoted in FIG. 1 by reference 35. In particular, each rail generally comprises a motor driven belt and pulley or chain system integrated with a support structure. Each printed circuit board is supported along its opposite side edges by first and a second rails, respectively, the printed circuit boards actually resting on the belts of the rails with support being provided by the support structure. Thus, as the belts move, the printed circuit boards are transported along the rails. The first and second rails on which the printed circuit boards are transported from what is commonly called a lane, and thus the printed circuit boards are said to be transported along the lane.
In many prior art systems, one rail forming a lane is typically fixed in position. The other rail forming the lane may also be fixed, may be manually adjustable, or may be automatically adjustable typically by coupling the rail to a ball screw and nut driven by a stepper motor, in order to accommodate printed circuit boards of different widths.
In order to increase manufacturing capacity, it has become desirable to increase the number of lanes so that more than one printed circuit board can be transported through the manufacturing system at a single time. Doing so by utilizing the prior art rail technology described above would thus require each lane to include a fixed rail and an adjustable rail having its own ball screw drive system. Thus, each additional lane would result in additional required component parts, thereby adding complexity and expense to the board transport system.